1. Field of the Invention
This invention relates to a method and apparatus for reducing oxides of nitrogen in the exhaust emissions of an internal combustion engine, and more particularly, to a new and improved method and apparatus for injecting atomic nitrogen into the exhaust of an internal combustion engine so that oxides of nitrogen in the exhaust are reduced to nitrogen and oxide.
2. Background of the Invention
If oxygen enriched air is used as part of the intake of an internal combustion engine, the engine's power density tends to be increased and the particulate emissions from the engine tend to be reduced. On the other hand, the use of such oxygen enriched air tends to increase the amount of oxides of nitrogen (NO.sub.X) that are present in the engine's exhaust. This increase in the amount of NO.sub.X in the engine's exhaust has concerned developers and manufacturers of internal combustion engines because legal regulations dealing with emissions from an internal combustion engine include specifications limiting the amount of NO.sub.X that may be present in such emissions. Consequently, the developers and manufacturers of internal combustion engines would like to obtain the advantages of using oxygen enriched air in the intake of an internal combustion engine, but at the same time would like to reduce the amount of NO.sub.X that is present in the engine's emissions.
One way of reducing NO.sub.X in any stream of gas is to inject atomic nitrogen into the stream of gas. For example, an article entitled "Effect of nitrogen-containing plasmas on stability, NO formation and sooting of flames" by J. C. Hilliard and F. J. Weinberg appearing in Nature, Vol. 259, page 556 (Feb. 19, 1976) indicates that nitrogen atoms from a plasma can be injected into a fast flowing stream of nitric oxide in argon and synthetic exhaust gas mixes. The article further states (page 557) that "[r]eductions in nitric oxide from 3,000 p.p.m. to a residual 80 p.p.m. were readily obtained in flows up to 250 1 min.sup.-1." A problem associated with the injecting of atomic nitrogen in the exhaust of an automobile engine is obtaining the atomic nitrogen to inject into the exhaust. One of the most common sources of atomic nitrogen is ammonia (NH.sub.3), but at the present time, it is not practical to store in an automobile that source of atomic nitrogen.
Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for reducing NO.sub.X emissions in the exhaust of an internal combustion engine.
It is another object of the present invention to provide a new and improved method and apparatus for injecting atomic nitrogen into the exhaust of an internal combustion engine to thereby cause oxides of nitrogen present in that exhaust to be reduced to nitrogen and oxygen.
It is yet another object of the present invention to provide a new and improved method and apparatus for reducing the amount of NO.sub.X in the emissions from an internal combustion engine by injecting atomic nitrogen into the exhaust of an internal combustion engine which atomic nitrogen is formed by subjecting to a corona or arc discharge nitrogen enriched air produced by a selectively permeable membrane.